This description relates to a backlight unit having light emitting diodes and a method for manufacturing the same
Typically, a light emitting diode (LED) is used by being optically coupled with a dome type lens according to its intrinsic characteristic.
Although many researches have been conducted on use of the light emitting diode onto a backlight unit of a liquid crystal display (LCD), it has become apparent that the thickness of the backlight unit has to be increased to embody an even optical characteristic of the light emitting diode in the backlight unit.
The thickness of the backlight unit tends to increase because of necessity of existence of a space if white light emitted from the light emitting diode is supposed to be evenly combined, e.g., bringing about creation of a disadvantage in which thickness of a liquid crystal display system is increased.
In order to overcome the afore-mentioned disadvantage, attempts have been recently made to package a backlight unit of a liquid crystal display using a light emitting diode package from which light is emitted from a side thereof (hereinafter referred to as a lateral light emitting diode package) as shown in FIG. 1.
FIG. 1 is a schematic perspective view of a lateral light emitting diode package, where the light emitting diode is bonded to a slug, and the slug is laterally positioned with leads 31 and 32 to be electrically bonded to the light emitting diode.
The light emitting diode and the slug are molded by molding means 40 to allow a light emitting surface of the light emitting diode and the leads 31 and 32 to be exposed outside, and a lens 20 encompassing the light emitting diode is bonded to the molding means. If the lateral light emitting diode package is employed as a light source of the liquid crystal display, a small amount of light is emitted from the center of the lateral light emitting diode package to prevent remaining light emitted from the light emitting diode from being incident on a lateral surface of the light emitting diode package, resulting in limit of manufacturing a uniform planar light source.
The emission of light from the center of the lateral light emitting diode package thus described causes an occurrence of a hot spot at the center of a pixel of the liquid crystal display, thereby resulting in degradation of picture quality of the display.
FIG. 2 is a schematic sectional view of a backlight unit of a liquid crystal display employed with a lateral light emitting diode package according to the prior art. In order to overcome the afore-mentioned disadvantage of the hot spot, there is used a hot spot baffle plate at the backlight unit of the liquid crystal display.
In other words, a backlight unit 90 of a liquid crystal display is such that hot spot baffle plates 80 are respectively disposed on each upper side of a plurality of lateral light emitting diode packages 50 packaged in a printed circuit board 60. A light guide plate 85 is disposed on the hot spot baffle plate 80, and a liquid crystal display 95 is disposed above the light guide plate to assemble the backlight unit 90 and liquid crystal display 95.
However, the backlight unit 90 thus constructed has a disadvantage of assembly process being complicated because an assembly job is involved with placing of the hot spot baffle plate 80 named a diverter on the plurality of lateral light emitting diode package 50.
Another disadvantage is that there appears a spot similar to a hot spot on a final screen of a liquid crystal display if there is an erroneous alignment of the hot spot baffle plate 80 on the plurality of lateral light emitting diode package 50.
Still another disadvantage is that the thickness of the liquid crystal display increases as much as that of the hot spot baffle plate 80.